ASCO GU 2019: A Multicentric Phase II Randomized Trial of Docetaxel plus Enzalutamide versus Docetaxel as First Line Chemotherapy for Patients with Metastatic Castration-Resistant Prostate Cancer: CHEIRON Study

San Francisco, CA ( Docetaxel and enzalutamide have previously been demonstrated to be effective in the treatment of metastatic castrate resistant prostate cancer (mCRPC). In this multi-institutional, Italian study, it was theorized that combination therapy would increase efficacy as first line therapy in patients with mCRPC.

mCRPC patients with good performance status were randomized to docetaxel 75mg/m2 D1 Q 3 weeks with prednisone 5mg BID for 8 courses alone or with enzalutamide 160mg daily for 24 weeks. All patients were continued on androgen deprivation therapy (ADT). Included patients were stratified for the existence of pain and visceral metastatic disease, with the primary endpoint of disease progression at 6 months. Secondary endpoints included overall response rate, biochemical response, progression free survival, safety, pain and quality of life.

246 patients were randomized (120 docetaxal + enzalutamide vs 126 docetaxel alone). Patient characteristics in both treatment groups were similar. At 6 months, the rates progression free survival was superior in the combination cohort compared to docetaxel alone (89% vs 73%; p=0.002). At a 20 month follow up, the median progression free survival was 10.1 months in the combination cohort compared to 9.1 months in the docetaxel only group (p<0.01). Overall survival was similar in both treatment cohorts (p=0.5). The combination cohort also had a greater percentage of patients with a PSA reduction >50%. No differences were noted in objective response rate. Toxicities were greater in the combination group, with the most common of which being fatigue (12.5%).

In conclusion, this is the first randomized trials combining docetaxel with an enzalutamide. It demonstrated that combination therapy was feasible, safe, and with certain endpoints provided improved disease control. Future clinical trials are needed to better assess docetaxel and enzalutamide, amongst other combination therapies.

Presented by: Orazio Caffo, MD, Santa Chiara Hospital, Trento, Italy

Written by:David B. Cahn, DO, MBS, @dbcahn, Fox Chase Cancer Center at the 2019 American Society of Clinical Oncology Genitourinary Cancers Symposium, (ASCO GU) #GU19, February 14-16, 2019 - San Francisco, CA